Toshiba's plans to put on sale worldwide next year its second generation of TVs that boast the ability to display images that exceed today's high-definition sets.

The TVs have four times the resolution of HD: 3840 pixels by 2160 pixels versus 1920 pixels by 1080 pixels; and the technology is collectively called "4K" because of the almost 4,000-pixel horizontal resolution.

Toshiba's three upcoming 4K models will be available in the spring of 2013, Masahiko Fukakushi, president and CEO of Toshiba’s digital products division, said at a Tokyo news conference on Thursday.

One of the three TVs will be an 84-inch model, one will be in the 60-inch range and the third in the 50-inch range. Pricing will also be announced closer to launch but will be competitive with other companies, Fukakushi said.

Toshiba's first generation 4K TV, a 55-inch model, is currently on sale in Japan at 750,000 yen (£5,959/US$9,650). Earlier Thursday, Sony said it will sell an 84-inch 4K television in Japan from November 23 for 1.68 million yen.

But while Toshiba and its rivals are rushing to put 4K TVs on the market, a rather important question remains unanswered : where will consumers get 4K content?

At present only the movie industry has started the shift to 4K, with several major hit movies already filmed at the resolution. But there's no consumer-level delivery method to get that content to homes with 4K televisions.

TV broadcasters have only recently spent billions of dollars upgrading to high definition and a further upgrade to 4K would mean most of their new equipment will have to be scrapped so that's unlikely. The Blu-ray Disc format hasn't been extended to 4K either.

A possibility exists with Internet-based delivery, but the extra resolution in 4K content means file sizes are huge and transmission of a single movie could take many hours.

So, for now, TV makers are relying on up-conversion. It's a trick that involves running high-definition content through a software algorithm to create a higher-resolution version. The quality isn't the same as if the original 4K content was viewed, but it's better than HD, said Toshiba.

With delivery of 4K content possibly years away, up conversion could be important. Toshiba has been working on custom chips to handle the work, something that it expects will give its TVs an edge over those from competitors.

Prototypes of Toshiba's 4K TVs are expected to be on show at next week's Ceatec exhibition in Makuhari, just outside of Tokyo. Ceatec opens on Tuesday.